1. Field of the Invention
The present invention relates to a transmission used to power a farm tractor, namely, in drawing PTO output together with travelling output of a tractor. More particularly, the invention relates to a transmission for a farm tractor designed to generate an output efficiently and easily by carrying out its speed changing steps or shifting in multiple steps.
2. Description of the Prior Art
It is a recent trend that the transmissions of their farm tractors carry out their speed changing steps in multiple steps so that their moving speed may be fractionalized to generate more efficient outputs.
In the conventional transmission, however, each speed changing step involves gears of different specifications and sizes, so that their shapes are complicated and manufacturing costs are accordingly high. Moreover, disassembly work for maintenance is not so easy so that a problem is also encountered in equipment control.
In order to solve such problems, an application for a Korean patent No. 90-22141 (the same applicant) discloses a transmission provide an output of 12 forward speeds, 4 independent PTO speeds and ground PTO by repeatedly forming the number of speed changing steps of a group of gears having the same number of teeth. However, the number of speed changing steps is so small that the moving speed of a tractor is not fractionalized and enormous power is consumed in bumpy or sloped or geologically rough terrain and a strain is thereby put on the equipment.